61 research outputs found
Tracking Topology Dynamicity for Link Prediction in Intermittently Connected Wireless Networks
Through several studies, it has been highlighted that mobility patterns in
mobile networks are driven by human behaviors. This effect has been
particularly observed in intermittently connected networks like DTN (Delay
Tolerant Networks). Given that common social intentions generate similar human
behavior, it is relevant to exploit this knowledge in the network protocols
design, e.g. to identify the closeness degree between two nodes. In this paper,
we propose a temporal link prediction technique for DTN which quantifies the
behavior similarity between each pair of nodes and makes use of it to predict
future links. We attest that the tensor-based technique is effective for
temporal link prediction applied to the intermittently connected networks. The
validity of this method is proved when the prediction is made in a distributed
way (i.e. with local information) and its performance is compared to well-known
link prediction metrics proposed in the literature.Comment: Published in the proceedings of the 8th International Wireless
Communications and Mobile Computing Conference (IWCMC), Limassol, Cyprus,
201
The impact of message replication on the performance of opportunistic networks for sensed data collection
Opportunistic networks (OppNets) provide a scalable solution for collecting delay-tolerant data from sensors to their respective gateways. Portable handheld user devices contribute significantly to the scalability of OppNets since their number increases according to user population and they closely follow human movement patterns. Hence, OppNets for sensed data collection are characterised by high node population and degrees of spatial locality inherent to user movement. We study the impact of these characteristics on the performance of existing OppNet message replication techniques. Our findings reveal that the existing replication techniques are not specifically designed to cope with these characteristics. This raises concerns regarding excessive message transmission overhead and throughput degradations due to resource constraints and technological limitations associated with portable handheld user devices. Based on concepts derived from the study, we suggest design guidelines to augment existing message replication techniques. We also follow our design guidelines to propose a message replication technique, namely Locality Aware Replication (LARep). Simulation results show that LARep achieves better network performance under high node population and degrees of spatial locality as compared with existing techniques
Routing protocol optimization in challenged multihop wireless networks
Durant ces derniĂšres annĂ©es, de nombreux travaux de recherches ont Ă©tĂ© menĂ©s dans le domaine des rĂ©seaux multi-sauts sans fil Ă contraintes (MWNs: Multihop Wireless Networks). GrĂące Ă l'Ă©volution de la technologie des systĂšmes mico-electro-mĂ©chaniques (MEMS) et, depuis peu, les nanotechnologies, les MWNs sont une solution de choix pour une variĂ©tĂ© de problĂšmes. Le principal avantage de ces rĂ©seaux est leur faible coĂ»t de production qui permet de dĂ©velopper des applications ayant un unique cycle de vie. Cependant, si le coĂ»t de fabrication des nĆuds constituant ce type de rĂ©seaux est assez faible, ces nĆuds sont aussi limitĂ©s en capacitĂ© en termes de: rayon de transmission radio, bande passante, puissance de calcul, mĂ©moire, Ă©nergie, etc. Ainsi, les applications qui visent l'utilisation des MWNs doivent ĂȘtre conçues avec une grande prĂ©caution, et plus spĂ©cialement la conception de la fonction de routage, vu que les communications radio constituent la tĂąche la plus consommatrice d'Ă©nergie.Le but de cette thĂšse est d'analyser les diffĂ©rents dĂ©fis et contraintes qui rĂ©gissent la conception d'applications utilisant les MWNs. Ces contraintes se rĂ©partissent tout le long de la pile protocolaire. On trouve au niveau application des contraintes comme: la qualitĂ© de service, la tolĂ©rance aux pannes, le modĂšle de livraison de donnĂ©es au niveau application, etc. Au niveau rĂ©seau, on peut citer les problĂšmes de la dynamicitĂ© de la topologie rĂ©seau, la prĂ©sence de trous, la mobilitĂ©, etc. Nos contributions dans cette thĂšse sont centrĂ©es sur l'optimisation de la fonction de routage en considĂ©rant les besoins de l'application et les contraintes du rĂ©seau. PremiĂšrement, nous avons proposĂ© un protocole de routage multi-chemin "en ligne" pour les applications orientĂ©es QoS utilisant des rĂ©seaux de capteurs multimĂ©dia. Ce protocole repose sur la construction de multiples chemins durant la transmission des paquets vers leur destination, c'est-Ă -dire sans dĂ©couverte et construction des routes prĂ©alables. En permettant des transmissions parallĂšles, ce protocole amĂ©liore la transmission de bout-en-bout en maximisant la bande passante du chemin agrĂ©gĂ© et en minimisant les dĂ©lais. Ainsi, il permet de rĂ©pondre aux exigences des applications orientĂ©es QoS.DeuxiĂšmement, nous avons traitĂ© le problĂšme du routage dans les rĂ©seaux mobiles tolĂ©rants aux dĂ©lais. Nous avons commencĂ© par Ă©tudier la connectivitĂ© intermittente entre les diffĂ©rents et nous avons extrait un modĂšle pour les contacts dans le but pouvoir prĂ©dire les future contacts entre les nĆuds. En se basant sur ce modĂšle, nous avons proposĂ© un protocole de routage, qui met Ă profit la position gĂ©ographique des nĆuds, leurs trajectoires, et la prĂ©diction des futurs contacts dans le but d'amĂ©liorer les dĂ©cisions de routage. Le protocole proposĂ© permet la rĂ©duction des dĂ©lais de bout-en-bout tout en utilisant d'une maniĂšre efficace les ressources limitĂ©es des nĆuds que ce soit en termes de mĂ©moire (pour le stockage des messages dans les files d'attentes) ou la puissance de calcul (pour l'exĂ©cution de l'algorithme de prĂ©diction).Finalement, nous avons proposĂ© un mĂ©canisme de contrĂŽle de la topologie avec un algorithme de routage des paquets pour les applications orientĂ©s Ă©vĂšnement et qui utilisent des rĂ©seaux de capteurs sans fil statiques. Le contrĂŽle de la topologie est rĂ©alisĂ© Ă travers l'utilisation d'un algorithme distribuĂ© pour l'ordonnancement du cycle de service (sleep/awake). Les paramĂštres de l'algorithme proposĂ© peuvent ĂȘtre rĂ©glĂ©s et ajustĂ©s en fonction de la taille du voisinage actif dĂ©sirĂ© (le nombre moyen de voisin actifs pour chaque nĆud). Le mĂ©canisme proposĂ© assure un compromis entre le dĂ©lai pour la notification d'un Ă©vĂ©nement et la consommation d'Ă©nergie globale dans le rĂ©seau.Great research efforts have been carried out in the field of challenged multihop wireless networks (MWNs). Thanks to the evolution of the Micro-Electro-Mechanical Systems (MEMS) technology and nanotechnologies, multihop wireless networks have been the solution of choice for a plethora of problems. The main advantage of these networks is their low manufacturing cost that permits one-time application lifecycle. However, if nodes are low-costly to produce, they are also less capable in terms of radio range, bandwidth, processing power, memory, energy, etc. Thus, applications need to be carefully designed and especially the routing task because radio communication is the most energy-consuming functionality and energy is the main issue for challenged multihop wireless networks.The aim of this thesis is to analyse the different challenges that govern the design of challenged multihop wireless networks such as applications challenges in terms of quality of service (QoS), fault-tolerance, data delivery model, etc., but also networking challenges in terms of dynamic network topology, topology voids, etc. Our contributions in this thesis focus on the optimization of routing under different application requirements and network constraints. First, we propose an online multipath routing protocol for QoS-based applications using wireless multimedia sensor networks. The proposed protocol relies on the construction of multiple paths while transmitting data packets to their destination, i.e. without prior topology discovery and path establishment. This protocol achieves parallel transmissions and enhances the end-to-end transmission by maximizing path bandwidth and minimizing the delays, and thus meets the requirements of QoS-based applications. Second, we tackle the problem of routing in mobile delay-tolerant networks by studying the intermittent connectivity of nodes and deriving a contact model in order to forecast future nodes' contacts. Based upon this contact model, we propose a routing protocol that makes use of nodes' locations, nodes' trajectories, and inter-node contact prediction in order to perform forwarding decisions. The proposed routing protocol achieves low end-to-end delays while using efficiently constrained nodes' resources in terms of memory (packet queue occupancy) and processing power (forecasting algorithm). Finally, we present a topology control mechanism along a packet forwarding algorithm for event-driven applications using stationary wireless sensor networks. Topology control is achieved by using a distributed duty-cycle scheduling algorithm. Algorithm parameters can be tuned according to the desired node's awake neighbourhood size. The proposed topology control mechanism ensures trade-off between event-reporting delay and energy consumption.BORDEAUX1-Bib.electronique (335229901) / SudocSudocFranceF
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Trust Management for P2P application in Delay Tolerant Mobile Ad-hoc Networks. An Investigation into the development of a Trust Management Framework for Peer to Peer File Sharing Applications in Delay Tolerant Disconnected Mobile Ad-hoc Networks.
Security is essential to communication between entities in the internet. Delay tolerant and disconnected Mobile Ad Hoc Networks (MANET) are a class of networks characterized by high end-to-end path latency and frequent end-to-end disconnections and are often termed as challenged networks. In these networks nodes are sparsely populated and without the existence of a central server, acquiring global information is difficult and impractical if not impossible and therefore traditional security schemes proposed for MANETs cannot be applied. This thesis reports trust management schemes for peer to peer (P2P) application in delay tolerant disconnected MANETs. Properties of a profile based file sharing application are analyzed and a framework for structured P2P overlay over delay tolerant disconnected MANETs is proposed. The framework is implemented and tested on J2ME based smart phones using Bluetooth communication protocol. A light weight Content Driven Data Propagation Protocol (CDDPP) for content based data delivery in MANETs is presented. The CDDPP implements a user profile based content driven P2P file sharing application in disconnected MANETs. The CDDPP protocol is further enhanced by proposing an adaptive opportunistic multihop content based routing protocol (ORP). ORP protocol considers the store-carry-forward paradigm for multi-hop packet delivery in delay tolerant MANETs and allows multi-casting to selected number of nodes. Performance of ORP is compared with a similar autonomous gossiping (A/G) protocol using simulations. This work also presents a framework for trust management based on dynamicity aware graph re-labelling system (DA-GRS) for trust management in mobile P2P applications. The DA-GRS uses a distributed algorithm to identify trustworthy nodes and generate trustable groups while isolating misleading or untrustworthy nodes. Several simulations in various environment settings show the effectiveness of the proposed framework in creating trust based communities. This work also extends the FIRE distributed trust model for MANET applications by incorporating witness based interactions for acquiring trust ratings. A witness graph building mechanism in FIRE+ is provided with several trust building policies to identify malicious nodes and detect collusive behaviour in nodes. This technique not only allows trust computation based on witness trust ratings but also provides protection against a collusion attack. Finally, M-trust, a light weight trust management scheme based on FIRE+ trust model is presented
Conception dâun support de communication opportuniste pour les services pervasifs
The vision of pervasive computing of building interactive smart spaces in the physical environment is gradually heading from the research domain to reality. Computing capacity is moving beyond personal computers to many day-to-day devices, and these devices become, thanks to multiple interfaces, capable of communicating directly with one another or of connecting to the Internet.In this thesis, we are interested in a kind of pervasive computing environment that forms what we call an Intermittently Connected Hybrid Network (ICHN). An ICHN is a network composed of two parts: a fixed and a mobile part. The fixed part is formed of some fixed infostations (potentially connected together with some fixed infrastructure, typically the Internet). The mobile part, on the other hand, is formed of smartphones carried by nomadic people. While the fixed part is mainly stable, the mobile part is considered challenging and form what is called an Opportunistic Network. Indeed, relying on short-range communication means coupled with the free movements of people and radio interferences lead to frequent disconnections. To perform a network-wide communication, the "store, carry and forward" approach is usually applied. With this approach, a message can be stored temporarily on a device, in order to be forwarded later when circumstances permit. Any device can opportunistically be used as an intermediate relay to facilitate the propagation of a message from one part of the network to another. In this context, the provisioning of pervasive services is particularly challenging, and requires revisiting important components of the provisioning process, such as performing pervasive service discovery and invocation with the presence of connectivity disruptions and absence of both end-to-end paths and access continuity due to user mobility. This thesis addresses the problems of providing network-wide service provisioning in ICHNs and proposes solutions for pervasive service discovery, invocation and access continuity. Concerning service discovery challenge, we propose TAO-DIS, a service discovery protocol that performs an automatic and fast service discovery mechanism. TAO-DIS takes into account the hybrid nature of an ICHN and that the majority of services are provided by infostations. It permits mobile users to discover all the services in the surrounding environment in order to identify and choose the most convenient ones. To allow users to interact with the discovered services, we introduce TAO-INV. TAO-INV is a service invocation protocol specifically designed for ICHNs. It relies on a set of heuristics and mechanisms that ensures performing efficient routing of messages (both service requests and responses) between fixed infostations and mobile clients while preserving both low values of overhead and round trip delays. Since some infostations in the network might be connected, we propose a soft handover mechanism that modifies the invocation process in order to reduce service delivery delays. This handover mechanism takes into consideration the opportunistic nature of the mobile part of the ICHN. We have performed various experiments to evaluate our solutions and compare them with other protocols designed for ad hoc and opportunistic networks. The obtained results tend to prove that our solutions outperform these protocols, namely thanks to the optimizations we have developed for ICHNs. In our opinion, building specialized protocols that benefit from techniques specifically designed for ICHNs is an approach that should be pursued, in complement with research works on general-purpose communication protocolsLa vision de l'informatique ubiquitaire permettant de construire des espaces intelligents interactifs dans l'environnement physique passe, peu Ă peu, du domaine de la recherche Ă la rĂ©alitĂ©. La capacitĂ© de calcul ne se limite plus Ă l'ordinateur personnel mais s'intĂšgre dans de multiples appareils du quotidien, et ces appareils deviennent, grĂące Ă plusieurs interfaces, capables de communiquer directement les uns avec les autres ou bien de se connecter Ă Internet.Dans cette thĂšse, nous nous sommes intĂ©ressĂ©s Ă un type d'environnement cible de l'informatique ubiquitaire qui forme ce que nous appelons un rĂ©seau hybride Ă connexions intermittentes (ICHN). Un ICHN est un rĂ©seau composĂ© de deux parties : une partie fixe et une partie mobile. La partie fixe est constituĂ©e de plusieurs infostations fixes (potentiellement reliĂ©es entre elles avec une infrastructure fixe, typiquement l'Internet). La partie mobile, quant Ă elle, est constituĂ©e de smartphones portĂ©s par des personnes nomades. Tandis que la partie fixe est principalement stable, la partie mobile pose un certain nombre de dĂ©fis propres aux rĂ©seaux opportunistes. En effet, l'utilisation de moyens de communication Ă courte portĂ©e couplĂ©e Ă des dĂ©placements de personnes non contraints et Ă des interfĂ©rences radio induit des dĂ©connexions frĂ©quentes. Le concept du "store, carry and forward" est alors habituellement appliquĂ© pour permettre la communication sur l'ensemble du rĂ©seau. Avec cette approche, un message peut ĂȘtre stockĂ© temporairement sur un appareil avant d'ĂȘtre transfĂ©rĂ© plus tard quand les circonstances sont plus favorables. Ainsi, n'importe quel appareil devient un relai de transmission opportuniste qui permet de faciliter la propagation d'un message dans le rĂ©seau. Dans ce contexte, la fourniture de services est particuliĂšrement problĂ©matique, et exige de revisiter les composants principaux du processus de fourniture, tels que la dĂ©couverte et l'invocation de service, en prĂ©sence de ruptures de connectivitĂ© et en l'absence de chemins de bout en bout. Cette thĂšse aborde les problĂšmes de fourniture de service sur l'ensemble d'un ICHN et propose des solutions pour la dĂ©couverte de services, l'invocation et la continuitĂ© d'accĂšs. En ce qui concerne le dĂ©fi de la dĂ©couverte de services, nous proposons TAO-DIS, un protocole qui met en Ćuvre un mĂ©canisme automatique et rapide de dĂ©couverte de services. TAO-DIS tient compte de la nature hybride d'un ICHN et du fait que la majoritĂ© des services sont fournis par des infostations. Il permet aux utilisateurs mobiles de dĂ©couvrir tous les services dans l'environnement afin d'identifier et de choisir les plus intĂ©ressants. Pour permettre aux utilisateurs d'interagir avec les services dĂ©couverts, nous introduisons TAO-INV. TAO-INV est un protocole d'invocation de service spĂ©cialement conçu pour les ICHN. Il se fonde sur un ensemble d'heuristiques et de mĂ©canismes qui assurent un acheminement efficace des messages (des requĂȘtes et des rĂ©ponses de services) entre les infostations fixes et les clients mobiles tout en conservant un surcoĂ»t et des temps de rĂ©ponses rĂ©duits. Puisque certaines infostations dans le rĂ©seau peuvent ĂȘtre reliĂ©es entre elles, nous proposons un mĂ©canisme de continuitĂ© d'accĂšs (handover) qui modifie le processus d'invocation pour rĂ©duire les dĂ©lais de dĂ©livrance. Dans sa dĂ©finition, il est tenu compte de la nature opportuniste de la partie mobile de l'ICHN. Nous avons menĂ© diverses expĂ©rimentations pour Ă©valuer nos solutions et les comparer Ă d'autres protocoles conçus pour des rĂ©seaux ad hoc et des rĂ©seaux opportunistes. Les rĂ©sultats obtenus tendent Ă montrer que nos solutions surpassent ces autres protocoles, notamment grĂące aux optimisations que nous avons dĂ©veloppĂ©es pour les ICHN. Ă notre avis, construire des protocoles spĂ©cialisĂ©s qui tirent parti des techniques spĂ©cifiquement conçues pour les ICHN est une approche Ă poursuivre en complĂ©ment des recherches sur des protocoles de communication polyvalent
Survey on RPL enhancements: a focus on topology, security and mobility
International audienceA few years ago, the IPv6 Routing Protocol for Low-power and Lossy Networks (RPL) was proposed by IETF as the routing standard designed for classes of networks in which both nodes and their interconnects are constrained. Since then, great attention has been paid by the scientific and industrial communities for the protocol evaluation and improvement. Indeed, depending on applications scenarios, constraints related to the target environments or other requirements, many adaptations and improvements can be made. So, since the initial release of the standard, several implementations were proposed, some targeting specific optimization goals whereas others would optimize several criteria while building the routing topology. They include, but are not limited to, extending the network lifetime, maximizing throughput at the sink node, avoiding the less secured nodes, considering nodes or sink mobility. Sometimes, to consider the Quality of Service (QoS), it is necessary to consider several of those criteria at the same time. This paper reviews recent works on RPL and highlights major contributions to its improvement, especially those related to topology optimization, security and mobility. We aim to provide an insight into relevant efforts around the protocol, draw some lessons and give useful guidelines for future developments
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